The present invention relates to organopolysiloxane compositions which can be crosslinked by addition of Si-bonded hydrogen onto an aliphatic carbonxe2x80x94carbon multiple bond, their preparation and their use.
EP-A-316 696 (Wacker Silicones Co.; published on May 24, 1989) describes organopolysiloxane compositions which can be crosslinked by condensation in which surface-treated aluminum hydroxide is used as an additional component in order to improve the electrical properties of the rubber obtained after crosslinkng. EP-A-586 153 (General Electric Co.; published on Mar. 9, 1994) discloses crosslinkable siloxane compositions which comprise additional fillers, such as calcium silicate, aluminum oxide and ceramic beads, which, in conjunction with alkoxy silanes, improves the mechanical properties, in particular the tear propagation resistance, of silicone rubbers.
The invention relates to crosslinkable organopolysiloxane compositions which comprise
(1) an organopolysiloxane which contains SiC-bonded radicals with aliphatic carbonxe2x80x94carbon multiple bonds, and
(2) an organopolysiloxane with a Si-bonded hydrogen atom or, instead of (1) and (2)
(3) an organopolysiloxane which contains a SiC-bonded radical with aliphatic carbonxe2x80x94carbon multiple bonds and Si-bonded hydrogen atoms,
(4) a catalyst which promotes the addition of Si-bonded hydrogen onto an aliphatic multiple bond,
(5) a reinforcing filler
(6) a non-reinforcing filler having an average particle diameter of less than 30 xcexcm and a BET surface area of less than 30 m2/g and, optionally, further substances.
If the composition according to the invention is a two-component silicone rubber composition, the two components of the silicone rubber compositions according to the invention can comprise all the constituents in any desired combination, with the proviso that one component does not simultaneously comprise siloxanes with an aliphatic multiple bond, siloxanes with Si-bonded hydrogen and the catalyst.
In the context of the present invention, the term organopolysiloxanes is also to be understood as meaning polymeric, oligomeric and dimeric siloxanes.
The organopolysiloxane compositions according to the invention have a content of organic solvent of not more than 3% by weight, preferably not more than 2% by weight, the compositions being, in particular, free from organic solvent
The siloxanes (1) and (2) or (3) used in the compositions according to the invention are chosen, such that crosslinking is possible. Thus, for example, siloxane (1) contains at least two aliphatically unsaturated radicals and siloxane (2) contains at least three Si-bonded hydrogen atoms, or siloxane (1) contains at least three aliphatically unsaturated radicals and siloxane (2) contains at least two Si-bonded hydrogen atoms, or, instead of siloxane (1) and (2), siloxane (3) which contains aliphatically unsaturated radicals and Si-bonded hydrogen atoms in the above mentioned ratios is used.
Organopolysiloxanes (1) which contain SiC-bonded radicals with aliphatic carbonxe2x80x94carbon multiple bonds are linear or branched organopolysiloxanes comprising units of the formula                               R          a                ⁢                  R          b          1                ⁢        S        ⁢                  xe2x80x83                ⁢        i        ⁢                  xe2x80x83                ⁢                  O                                    4              -              a              -              b                        2                                              (I)            
in which
R is a monovalent SiC-bonded, optionally substituted hydrocarbon radical which has 1 to 18 carbon atoms and is free from aliphatic carbonxe2x80x94carbon multiple bonds,
R1 is a monovalent SiC-bonded hydrocarbon radical with an aliphatic carbonxe2x80x94carbon multiple bond,
a is 0, 1, 2 or 3 and
b is 0, 1 or 2,
with the proviso that the sum a+b is less than or equal to 3 and at least two radicals R1 are present per molecule.
Examples of radicals R are alkyl radicals, such as the methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl and tert-pentyl radical, hexyl radicals, such as the n-hexyl radical, heptyl radicals, such as the n-heptyl radical, octyl radicals, such as the n-octyl radical and isooctyl radicals, such as the 2,2,4-trimethylpentyl radical, nonyl radicals, such as the n-nonyl radical, decyl radicals, such as the n-decyl radical, dodecyl radicals, such as the n-dodecyl radical, and octadecyl radicals, such as the n-octadecyl radical, cycloalkyl radicals, such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl radicals, aryl radicals, such as the phenyl, naphthyl, anthryl and phenanthryl radical, alkaryl radicals, such as o-, m- and p-tolyl radicals, xylyl radicals and ethylphenyl radicals, and aralkyl radicals, such as the benzyl radical and the xcex1- and the xcex2-phenylethyl radical.
Examples of substituted radicals R are halogenoalkyl radicals, such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2xe2x80x2,2xe2x80x2,2xe2x80x2-hexafluoroisopropyl radical and the heptafluoroisopropyl radical, and halogenoaryl radicals, such as the o-, m- and p-chlorophenyl radical.
The radical R is preferably a monovalent SiC-bonded hydrocarbon radical which has 1 to 6 carbon atoms and is free from aliphatic carbonxe2x80x94carbon multiple bonds, the methyl radical being preferred.
Examples of radicals R1 are alkenyl radicals, such as the vinyl, 5-hexenyl, cyclohexenyl, 1-propenyl, allyl, 3-butenyl and 4-pentenyl radical, and alkynyl radicals, such as the ethynyl, propargyl and 1-propynyl radical.
The radical R1 is preferably alkenyl radicals, the vinyl radical being more preferred.
The siloxanes (1) used according to the invention are preferably those of the formula
R1xSiR3-xO(SiR2O)n(SiR1RO)mSiR3-xR1xxe2x80x83xe2x80x83(II) 
in which
R and R1 have the meaning given above,
x is 0, 1, 2 or 3, preferably 1,
m is 0 or a number from 1 to 50 and
n is a number from 50 to 100,000,
with the proviso that the siloxanes of formula (II) contain at least two radicals R1 per molecule and the n units (SiR2O) and the m units (SiR1RO) can be distributed in the molecule as desired, for example as a block or randomly.
The organopolysiloxanes (1) preferably have an average viscosity of 100 to 200,000 mm2/s, more preferably 200 to 100,000 mm2/s, at 25xc2x0 C.
The compositions according to the invention comprise siloxane (1) in amounts of 10% to 80% by weight, preferably 15% to 60% by weight.
Organopolysiloxanes (2) which contain Si-bonded hydrogen atoms and are used are linear, cyclic or branched organopolysiloxanes of units of the formula                               R          g          2                ⁢                  H          f                ⁢                  xe2x80x83                ⁢        S        ⁢                  xe2x80x83                ⁢        i        ⁢                  xe2x80x83                ⁢                  O                                    4              -              g              -              f                        2                                              (III)            
in which
R2 has the meaning given above for radical R,
g is 0, 1, 2 or 3 and
f is 0, 1 or 2,
with the proviso that the sum of g+f is less than or equal to 3 and at least 3 Si-bonded hydrogen atoms are present per molecule.
Examples of radical R2 are the examples mentioned for R, alkyl radicals having 1 to 6 carbon atoms being preferred and the methyl and phenyl radicals being more preferred.
In the siloxanes of units of formula (III), the units containing Si-bonded hydrogen can be arranged in a block or distributed randomly.
The organopolysiloxane (2) used according to the invention contains Si-bonded hydrogen in a range from 0.01% to 1.5% by weight, preferably 0.05% to 1.5% by weight, based on the total weight of the organopolysiloxane (2).
The organopolysiloxanes (2) have an average viscosity of 20 to 50,000 mm2/s, preferably 40 to 5000 mm2/s, in each case at 25xc2x0 C.
The siloxanes (2) used according to the invention are preferably essentially linear siloxanes having a chain length of not more than 1000 siloxane units.
The compositions according to the invention comprise siloxane (2) in amounts of 0.2% to 30% by weight, preferably 0.5% to 20% by weight, in particular 1% to 10% by weight.
The siloxanes (1) and (2) used according to the invention are commercially available products or can be prepared by processes customary in chemistry.
Instead of organopolysiloxanes (1) and (2), the compositions according to the invention can comprise organopolysiloxanes (3) which contain both aliphatic carbonxe2x80x94carbon multiple bonds and Si-bonded hydrogen atoms, although this is not preferred.
If siloxanes (3) are used, they are preferably those of units of the formulae             R      c        ⁢          SiO                        4          -          c                2              ,            R      d        ⁢          R      1        ⁢          SiO                        3          -          d                2              ⁢          xe2x80x83        ⁢    and    ⁢          xe2x80x83        ⁢          R      e        ⁢          HSiO                        3          -          e                2            
in which
R and R1 have the meaning given above,
c is 0, 1, 2 or 3,
d is 0, 1 or 2 and
e is 0, 1 or 2,
with the proviso that at least 2 radicals R1 and at least 3 Si-bonded hydrogen atoms or at least 3 radicals R1 and at least 2 Si-bonded hydrogen atoms are present per molecule.
Examples of organopolysiloxanes (3) are those of SiO4/2, R3SiO1/2, R2R1SiO1/2 and R2HSiO1/2 units, so-called MQ resins, where these resins can additionally contain RSiO3/2 and R2SiO units and R and R1 have the above mentioned meaning.
The organopolysiloxanes (3) have an average viscosity of 10 to 100,000 mm2/s at 25xc2x0 C., or are solids having molecular weights of 5000 to 50,000 g/mole.
Organopolysiloxanes (3) can be prepared by methods customary in chemistry.
The same catalysts which have been used for promoting crosslinking in the compositions to date which can be crosslinked by addition of Si-bonded hydrogen onto an aliphatic carbonxe2x80x94carbon multiple bond can be used as the catalyst (4) which promotes addition of Si-bonded hydrogen onto an aliphatic multiple bond.
Examples of catalysts (4) are metallic and finely divided platinum (platinum sol), ruthenium, rhodium, palladium and iridium, it being possible for these metals to be applied to solid supports, such as silicon dioxide, aluminum oxide, active charcoal, ceramic materials or mixed oxides or mixed hydroxides, although this is not preferred.
Other examples of catalysts (4) are compounds or complexes of these metals, such as platinum halides, for example PtCl4, H2PtDl6.6H2O and Na2PtCl4.4H2O, platinum-olefin complexes, platinum-alcohol complexes, such as, the so-called Speyers catalyst, platinum-alcoholate complexes, platinum-ether complexes, platinum-aldehyde complexes, platinum-ketone complexes, including reaction products of H2PtCl6.6H2O and cyclohexanone, platinum-vinylsiloxane complexes, in particular platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes with or without a content of organically bonded halogen, bis-(xcex3-picoline)-platinum dichloride, trimethylenedipyridine platinum dichloride, dicyclopentadieneplatinum dichloride, dimethyl-sulfoxide ethyleneplatinum (II) dichloride, reaction products of platinum tetrachloride with olefin and primary amine or secondary amine or primary and secondary amine, such as the reaction product of platinum tetrachloride, dissolved in 1-octene, with sec-butylamine, cyclooctadiene-platinum dichloride and norbornadiene-platinum dichloride, as well as ammonium-platinum complexes.
Platinum metals or compounds or complexes thereof, in particular platinum compounds or complexes, are used as catalysts (4) in the compositions according to the invention.
Catalysts (4) are used in amounts such that a platinum content of preferably 0.5 to 500 ppm by weight (=parts by weight per million parts by weight), in particular 3 to 300 ppm by weight, in each case based on the total weight of the composition according to the invention, results.
The reinforcing fillers (5) used according to the invention have a BET surface area of more than 50 m2/g, preferably more than 100 m2/g, more preferably more than 150 m2/g.
Examples of the reinforcing fillers (5) used according to the invention are pyrogenically prepared silicic acid, precipitated silicic acid or silicon-aluminum mixed oxides having a BET surface area of more than 50 m2/g. The fillers mentioned can be hydrophobized, for example by treatment with organosilanes or siloxanes or by etherification of hydroxyl groups to alkoxy groups.
The reinforcing fillers (5) used according to the invention are pyrogenically prepared silicic acids having a BET surface area of more than 100 m2/g, pyrogenically prepared silicic acids having a BET surface area of more than 150 m2/g being preferred.
The compositions according to the invention comprise reinforcing fillers (5) in amounts of 5% to 50% by weight, preferably 5% to 40% by weight, more preferably 5% to 20% by weight.
Examples of the non-reinforcing fillers (6) used according to the invention are powders of quartz, cristobalite, diatomaceous earth, calcium silicate, zirconium silicate, montmorillonites, such as bentonites, zeolites, including the molecular sieves, such as sodium aluminum silicate, metal oxides, such as aluminum oxide or zinc oxide or mixed oxides thereof, metal hydroxides, such as aluminum hydroxide, barium sulfate, calcium carbonate, gypsum, glass or plastics having a BET surface area of less than 30 m2/g and an average particle diameter of less than 30 xcexcm, metal oxides, silicates, metal hydroxides and carbonates being preferred and aluminum oxide, aluminum hydroxide and quartz powder being more preferred.
The average particle diameter of the non-reinforcing fillers (6) used according to the invention is less than 20 xcexcm, preferably 0.1 to 20 xcexcm.
The BET surface area of the non-reinforcing fillers (6) used according to the invention is preferably less than 20 m2/g, more preferably 2 to 20 m2/g.
The compositions according to the invention comprise non-reinforcing fillers (6) in amounts of 10% to 80% by weight, preferably 20% to 70% by weight, in particular 30% to 70% by weight.
The weight ratio of non-reinforcing filler (6) to reinforcing filler (5) in the compositions according to the invention is preferably 20:1 to 2:1, more preferably 12:1 to 4:1.
The non-reinforcing filler (6) and reinforcing filler (5) are commercially available products.
Optionally, the compositions according to the invention can comprise further substances which have been used to date in compositions which can be crosslinked by addition of Si-bonded hydrogen onto an aliphatic multiple bond, such as, inhibitors (7), adhesion promoters (8), siloxanes (9) other than the siloxane (1), (2) or (3), and additives (10).
Examples of inhibitors (7) are siloxanes containing vinyl groups, such as, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, benzotriazole, dialkylformamides, alkylthioureas, methyl ethyl ketoxime, organic and organosilicon compounds having a boiling point of at least 25xc2x0 C. under 1012 hPa and at least one aliphatic triple bond, such as 1-ethynylcyclohexan-1-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 2,5-di-methyl-3-hexyne-2,5-diol and 3,5-di ethyl-1-hexyn-3-ol, a mixture of diallyl maleate and vinyl acetate, and maleic acid monoesters.
The inhibitor (7) which is used optionally is preferably an organic alkynol or a siloxane containing vinyl groups, 1-ethynylcyclohexanol, 3-methyl-1-butyn-3-ol and disiloxanes containing vinyl groups being more preferred.
The compositions according to the invention comprise inhibitor (7), in amounts of 0.01% to 3% by weight, preferably 0.05% to 2% by weight, based on the composition according to the invention.
Examples of adhesion promoters (8) which are used, optionally, are silanes with hydrolyzable groups and SiC-bonded vinyl, acryloxy, methacryloxy, epoxide, acid anhydride, acid, ester or ether groups and partial and mixed hydrolyzates thereof, silanes with vinyl groups and silanes with epoxide groups which contain ethoxy or acetoxy groups as hydrolyzable radicals being preferred, and vinyltriethoxysilane, vinyltriacetoxysilane, epoxypropyltriethoxysilane and partial and mixed hydrolyzates thereof being more preferred.
The compositions according to the invention comprise adhesion promoters (8) in amounts of 0% to 5% by weight, preferably 1% to 3% by weight.
Examples of siloxanes (9) which are used, optionally, are organo-polysiloxanes of units of formula (I) or of formula (II) with, fewer than two aliphatically unsaturated radicals per molecule, organopolysiloxanes of units of formula (III) with no or, fewer than three Si-bonded hydrogen atoms per molecule, MT resins of the formula (R33SiO1/2)y(R3SiO3/2)z and MQ resins of the formula (R33SiO1/2)y(SiO4/2)z, in which R3 has a meaning given for the radical R or for R1 and the ratio of y:z can be chosen such that liquid or solid resins are present at room temperature.
The compositions according to the invention comprise siloxane (9) in amounts of 0% to 60% by weight preferably 0% to 40% by weight.
Examples of the additives (10) which are used, optionally, are soluble dyestuffs, inorganic or organic pigments, stabilizers, such as UV stabilizers, agents which trap free radicals and UV blockers, as long as these contain no groups which inhibit the addition of Si-bonded hydrogen onto an aliphatic multiple bond or are not complexing agents for the metals used as catalysts (4).
The nature and amount of the additives (10) which are to be used, optionally, essentially depend on the profile of requirements of the compositions according to the invention or of the vulcanizates formed therefrom and are known to the expert.
The compositions according to the invention comprise no constituents other than components (1) to (10).
Components (1) to (10) used according to the invention can in each case be an individual type of such a component or a mixture of at least two different types of such a component.
The compositions according to the invention have a viscosity of less than 300,000 mm2/s, preferably 50 to 200,000 mm2/s.
The compositions according to the invention are those which comprise
(1) an organopolysiloxane, which contains SiC-bonded radicals with aliphatic carbonxe2x80x94carbon multiple bonds, of units of formula (I), with the proviso that the sum a+b is less than or equal to 3 and at least 2 radicals R1 are present per molecule,
(2) an organopolysiloxane, which contains Si-bonded hydrogen atoms, of units of formula (III), with the proviso that the sum of g+f is less than or equal to 3 and at least 3 Si-bonded hydrogen atoms are present per molecule,
(4) platinum metals or compounds or complexes thereof,
(5) a reinforcing filler having a BET surface area of more than 50 m2/g,
(6) a non-reinforcing filler having an average particle diameter of less than 30 xcexcm and a BET surface area of less than 30 m2/g and
(7) an inhibitor.
The compositions according to the invention are those which comprise
(1) 10% to 80% by weight of organopolysiloxanes, which contain SiC-bonded radicals with aliphatic carbonxe2x80x94carbon multiple bonds, of formula (II), with the proviso that at least two radicals R1 are present per molecule,
(2) 0.5% to 20% by weight of organopolysiloxanes, which contain Si-bonded hydrogen atoms, of units of formula (III), with the proviso that the sum of g+f is less than or equal to 3 and at least 3 Si-bonded hydrogen atoms are present per molecule,
(4) platinum metals or compounds or complexes thereof in amounts such that a platinum content of preferably 0.5 to 500 ppm by weight (=parts by weight per million parts by weight), based on the total weight of the composition according to the invention, results,
(5) 5% to 50% by weight of reinforcing filler having a BET surface area of more than 50 m2/g,
(6) 10% to 80% by weight of non-reinforcing filler having an average particle diameter of less than 30 xcexcm and a BET surface area of less than 30 m2/g and
(7) 0.01% to 3% by weight of inhibitor.
The compositions according to the invention can be prepared by known processes, for example by simple mixing of the individual components.
The compositions according to the invention which can be crosslinked by addition of Si-bonded hydrogen onto an aliphatic multiple bond can be allowed to crosslink under the same conditions as the compositions known to date which can be crosslinked by a hydrosilylation reaction. These are preferably temperatures of 10xc2x0 to 300xc2x0 C., more preferably 20xc2x0 to 280xc2x0 C., in particular 20xc2x0 to 200xc2x0 C., and a pressure of 900 to 1100 hPa. However, higher or lower temperatures and pressures can also be used.
The present invention furthermore relates to shaped articles produced by crosslinking the compositions according to the invention.
The compositions according to the invention can be used in all instances where compositions based on organopolysiloxanes with Si-bonded hydrogen and aliphatically unsaturated radicals have been used to date, for example, as embedding compositions for electrical or electronic devices, as impression compositions or coating compositions or for the production of shaped articles, for example by the injection molding process, vacuum extrusion process, extrusion process, casting molding and compression molding. The compositions according to the invention are always used, in particular, if, on the basis of the profile of requirements, a silicone surface can advantageously be used but the typical blocking surface is to be avoided, such as, for example, surfaces of keyboards, toys, tools, medical articles, insulating hoses and coated textiles.
The most diverse substrates, such as plastics, glass fiber-reinforced plastics, silicone rubber, wood, mineral materials, metal, porcelain, glass, mineral fibers, such as glass fibers or rock wool and textiles, can be coated with the compositions according to the invention. Examples of textile substrates which can be coated with the compositions according to the invention are woven fabrics, knitted fabrics, nonwovens, braided materials and looped fabrics of naturally occurring and/or synthetic fibers, such as cotton, polyamide, polyester, polyethylene, polypropylene, polyurethane, silk and viscose. The textiles coated according to the invention can be used, for example, as electrical insulating covers, electrical insulating hoses, thermal insulations, electrical insulations, sports clothing, sports articles, such as sails, boat covers, rucksacks, tents and protective clothing, awnings, conveyor belts, compensators, foldable containers, inflatable textile containers, blinds or textile architecture.
The composition according to the invention can be applied in the customary manner, for example, by brushing, pouring, spraying, rolling, printing, knife-coating, slop-padding, dipping or screen printing, or by application with a so-called Meyer rod or with an airbrush After application of the composition according to the invention, the coated substrate is preferably exposed to elevated temperature, for example, between 20xc2x0 and 280xc2x0 C., for a residence time of 10 to 600 seconds. This can be performed continuously or discontinuously in corresponding heating ovens. The energy can be supplied in the form of hot air, radiation, heat transfer media or by direct contact with hot substrates.
The present invention also relates to a process for the production of coatings which comprises applying the composition according to the invention to the substrate and allowing it to crosslink at a temperature between 20xc2x0 and 28xc2x0 C.
The crosslinkable compositions according to the invention have the advantage that, after the crosslinking, they result in vulcanizates with surfaces with a dry hand, which do not have the so-called xe2x80x9cfroggy handxe2x80x9d.
The compositions according to the invention have the advantage that, after the crosslinking, they result in vulcanizates having non-blocking, anti-friction, non-abrasive and matt surfaces.
The compositions according to the invention have the advantage that they are easy to prepare and have excellent processing properties.
The compositions according to the invention have the advantage that they are essentially free from organic solvent.
The compositions according to the invention have the advantage that after the vulcanization, they result in surfaces of reduced coefficient of friction.
The process according to the invention for the production of coatings has the advantage that it is easy to carry out and coatings can be produced in a single working operation.
The process according to the invention for the production of coatings has the advantage that no undesirable solvent vapors form during the crosslinking.
The process according to the invention for the production of coatings also has the advantage that units which are customary in the textile coating industry can be used for processing the compositions according to the invention.
In the examples described below, all the parts data are based on the weight, unless stated otherwise. Unless stated otherwise, the examples below are carried out under a pressure of the surrounding atmosphere, under about 1000 hPa, and at room temperature, at about 20xc2x0 C., or at a temperature which is established when the reactants are brought together at room temperature without additional heating or cooling.
All the viscosity data below are based on a temperature of 25xc2x0 C.
The tear propagation resistance of the vulcanizates is determined in accordance with ASTM D624-B-91.
The Shore A hardness is determined in accordance with DIN (Deutsche Industrie Norm [German industrial standard]) 53505-87.
The tear strength is determined in accordance with DIN 53504-85S1.
The elongation at break is determined in accordance with DIN 53504-85S1.
The LOI (limiting oxygen index) is determined in accordance with ASTM D2863-70.
The coefficient of friction is determined in accordance with ASTM D1894.